PIs: Roel Neggers, Yaping Shao, Ulrich Löhnert

Recent studies underline that Arctic Amplification is closely coupled to the presence of Arctic low–level clouds. Consequently, this project aims to investigate the processes leading to the development, sustainment and decay of Arctic low–level clouds and cloud patterns, focusing on their micro–physical, macro–physical and dynamical properties as well as their interaction with heterogeneous surface properties. Our research strategy consists of an integrated approach of Large–Eddy resolving Simulations (LES) in combination with novel types of ground–based remote sensing. Insights gained through these activities will inspire parameterization improvement and development for weather and climate models, using Single Column Model (SCM) as well as Regional and Global Climate Model (RCM/GCM) simulations. The configuration of the LES will consist of Eulerian as well as Lagrangian realizations, with Eulerians covering long time–periods at fixed locations and Lagrangians designed to collocate with ship track and aircraft measurements. Specific topics of interest include (i) the representation of mixed–phase microphysics in models, (ii) the coupling of heterogeneous surfaces to clouds, (iii) the macrophysics and dynamics of clouds in cold–air outbreaks. LES will play a key role in these activities, providing virtual information on horizontal variability associated with boundary layer clouds and surface heterogeneity, but also being the subject of evaluation itself on aspects in which the LES approach is known to have shortcomings, i.e., concerning the parameterization of microphysical processes, which are suspected to significantly impact the macrophysics and dynamics of Arctic clouds. The upgrade of the Ny–Ålesund observatory (E02) plays an essential role in all activities within E03. Next to providing relevant, long–term measurements of Arctic low–level clouds, Ny–Ålesund opens new possibilities for looking into the details of Arctic mixed–phase microphysics by using cloud Doppler spectra observations in combination with passive radiometers. E03 will combine this observational data record and that of other Arctic observatories with observations from the Research Vessel (RV) Polarstern and the Polar 5 & 6 aircraft during dedicated measurement campaigns.